<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        html, body {
            padding: 0;
            margin: 0;
        }
    </style>
</head>
<body>
<div id="el1">
</div>

<button id="makeFloat"></button>
<button id="setClass"></button>
<button id="setAttr"></button>
<button id="setTextContent"></button>

<script>
    var div = document.getElementById('el1');

    document.getElementById('makeFloat').addEventListener('click', function () {
        window.setTimeout(function () {
            div.style.float = 'left';
        }, 200);
    });

    document.getElementById('setClass').addEventListener('click', function () {
        window.setTimeout(function () {
            div.className += 'hey';
        }, 150);
    });

    document.getElementById('setAttr').addEventListener('click', function () {
        window.setTimeout(function () {
            div.setAttribute('checked', true);
        }, 180);
    });

    document.getElementById('setTextContent').addEventListener('click', function () {
        window.setTimeout(function () {
            div.textContent = '42';
        }, 180);
    });
</script>

</body>
</html>
